Multi-Stage Power Amplifier Die Partitioning for Wider RF Bandwidth
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Solution Overview
Problem
Multi-stage power amplifiers face inefficiencies due to high impedance transformation ratios between driver and output amplifiers, leading to reduced overall efficiency and narrower bandwidth, primarily attributed to differences in gate widths and voltage operations across amplifier stages.
Innovation Solution
Implementing a power amplifier design with a driver amplifier formed using a lower voltage semiconductor fabrication process and an output amplifier using a higher voltage process, along with an inter-stage matching network, which includes wire bonds to reduce impedance transformation ratios and simplify matching networks, thereby improving line-up efficiency and RF bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single high-voltage fabrication process is used for both driver and output amplifiers, then voltage compatibility is maintained, but impedance transformation ratio increases and efficiency decreases
Solution Approach 1:
The power amplifier is segmented into two separate amplifier stages (driver and output) fabricated on different semiconductor dies using different voltage processes. The driver amplifier uses a first voltage fabrication process while the output amplifier uses a second voltage fabrication process, allowing each stage to be optimized independently for its specific voltage requirements and reducing overall power dissipation.
Solution Approach 2:
Different regions of the power amplifier system use different fabrication process characteristics. The driver amplifier region uses a first voltage process optimized for its operating conditions, while the output amplifier region uses a second voltage process optimized for high-power output, allowing each local region to have the quality needed for its specific function.
2Loss of energy
If driver amplifier gate width is increased, then impedance transformation ratio decreases and efficiency improves, but device area increases
Solution Approach 1:
The gate width of the driver amplifier is adjusted as a key parameter to optimize the impedance transformation ratio. By carefully selecting the gate width within constraints, the design achieves improved power dissipation characteristics while maintaining acceptable device area through the combined effect of using different fabrication processes for driver and output stages.
3Device complexity
If inter-stage matching network is simplified, then device complexity decreases and costs reduce, but impedance matching precision may worsen
Solution Approach 1:
The matching network is segmented and distributed across different interconnection structures between separate amplifier dies. Wire bonds and package parasitics are utilized as part of the matching solution, reducing the need for complex on-die matching networks while achieving adequate impedance matching through the combined effect of simplified individual sections.
Data Source
AI summary
Efficiency improvements for multi-stage power amplifiers are described. In one example, a power amplifier includes a driver amplifier formed on a first semiconductor die using a first semiconductor fabrication process, an output amplifier formed on a second semiconductor die using a second semiconductor fabrication process, and an inter-stage matching network formed between the driver amplifier and the output amplifier. The first semiconductor fabrication process is a lower voltage process and the second semiconductor fabrication process is a higher voltage process. The use of the two different fabrication processes leads to a number of advantages, including the simplification of the inter-stage matching network, increased radio frequency bandwidth, and improved line-up efficiency among the stages of the power amplifier.